masked loads?

[Matthias Kretz]

Hello Kay,

On Donnerstag, 21. Juli 2016 18:54:51 CEST Kay F. Jahnke wrote:
> Am 19.07.2016 um 10:10 schrieb Matthias Kretz:
> > Vector<T> x = {};
> > x(mask) = Vector<T>(mem);
> 
> If mem points to ordinary memory which contains less than
> Vector<T>::Size T, is it guaranteed to be safe to construct a Vector<T>
> from mem?

That's the problem. The load constructor will access all ::Size elements in 
memory. While it still may work without a crash, it is undefined behavior 
according to the C++ standard, so let's not go there.

I recommend you write a function to extend Vc. E.g.

SSE::Vector<float> maskedload(SSE::Mask<float> k, const float *mem) {
  return _mm_maskload_ps(mem, k.dataI());
}

Then overload the function for all the implementations you care for and submit 
the patch as an issue on GitHub. I'll consider merging it in some form.

Cheers,
  Matthias

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